It is known in the prior art of slidable window sash and frame construction to have vertical and horizontal sliding windows adapted to be pivoted out of the frame when desired. For tasks such as cleaning the window from within the building in which the window is installed, a pivoting window must be securely arrested from sliding at the pivot point to prevent sagging or complete dislodging of the sash from the frame.
Pivot mechanisms have included movable pins mounted on the edge of the sash which may be extended outwardly to engage holes in the frame about which the sash may be pivoted. U.S. Pat. No. 4,222,201 discloses a pivoting mechanism wherein a pair of spring biased pins are manually extended outward. Mating apertures in the tracks receive the pins, providing an axis of rotation. The sash may then be pivoted. After the window is pivoted back into the plane of the frame, the pins are retracted and secured in place by a screw to allow the sash to freely slide within the frame.
U.S. Pat. No. 5,058,321 discloses a mechanism wherein spring biased pivot pins are freed for selective extension into apertures formed in a frame by rotating said pins. The pins are retracted by rotation and secured in place by an arrangement of detents.
It is also known in the prior art to provide a pivoting arrangement which achieves automatic arresting of the sliding motion of a slider body in a track in response to the commencement of the pivoting of the window sash. U.S. Pat. No. 4,610,108 discloses such a device which incorporates a generally U-shaped spring member within a block, wherein a pin or strut extending from a window sash is connected. A cam member is incorporated in the block member which is rotatably engagable with the U-shaped member to lock the block in position upon pivoting the window sash. Although simple to operate, experience has shown that a pivot arrangement of this type may not develop adequate arresting strength and reliability.
U.S. Pat. No. 5,414,960 discloses a cam and frictional locking assembly in which rotation of the cam in a sliding block, slidably mounted within a track, produces lateral, or radial expansion and normal, or axial biasing of the slide block to frictionally engage four sides of the slide block with respective opposing track surfaces.